Method of and means for bending tubes



April 9, 1935.

L. W. SNELL METHOD OF AND MEANS FOR BENDING TUBES 2 sheets-sheet 1 FiledJuly 25, 1952 /NVENTOR 1 L. w- S/vl. L. 5v NCQ@ nrro e/vzn Y April9,1935. j LfwsN'ELL 1,996,838

n METHOD OF AND MEANS FOR BENDING TUBES Filed July 25, 1932 2sheets-sheei 2 Patented Apr. 9, 1935 UNITED STATES PATENT OFFICE1,996,833 METHOD oF AND MEANS Eon BENDING TUBES p Lester W. Snell,Alton, lll. Application July 25, 1932, Serial No. 624,405 17 Claims.(Cl. 153-32) This invention relates to methods of and means i forbending tubes, and the novel features may such as U-shaped return bends,elbows with end portions at various angles to each other, and also` v inmaking long continuous coils of tubing.

In performing an ordinary simple bending operation, a metal tube isstretched at the arc oi' greatest radius which is termed the outerportion of the bend, while the metal is compressed at the' inner portionof the bend, where the radius of the curve is shorter. The stretching inthis old method reduces the thickness of the metal at the outer portionof the bend, while the compression increases the thickness at the innerportion of the bend. As a consequence, the ordinary simple bendingoperation results in a bent tube that is non-uniform in thickness.

One of the objects of this invention is tobend the tubes whilepreventing undesirable variations in the thickness of the tube walls.

Another object is to accurately bend the tubes to a predeterminedcurvature and diameter.

A further object is to provide the bent tube with a smooth and uniformcircular outer face.

With the foregoing and other objects in view, the invention comprisesthe novel method, construction, combination and arrangement of partshereinafter more specifically described and illustrated in theaccompanying drawings, wherein is shown the preferred embodiment of theinvention. However, it is to be understood that the inventioncomprehends changes, variations `and modifications which come within thescopeof the claims hereunto appended.

Fig. 1 is a section illustrating a bending system embodying the featuresof this invention.

Fig. 2 is a transverse section on the line 2 2 in Fig. 1, showingvariations in the thickness of the tube to be bent.

Fig. 3 is a section on the line 3 3 in Fig. 1, showing the uniformthickness of the bents tube.

` Fig. 4 is a section on the line 4 4 in Fig. 1.

I Fig. 5 is a section on the line 5 5 in Fig. 1.

Fig. 6 is a side elevation on a smaller scale showing a hammer-operatingdevice.

Fig. 7 is a section taken approximately on the line 1 1 in Fig. 6.

Fig. 8 is a section taken approximately on the line 8 8 in Fig. 6. l

'Ihe apparatus shown `'to illustrate one form of the invention comprisesa forming die 9 made of two sections contacting with each other at theline I0 in Fig. 5, and alinedl by means of dowel pins I I, saicl diehaving a curved passageway I2,

through which the tube to give the desired curvature.

I3 indicates a tube adapted to be forced through the passageway I2. Inthe preferred form of theinvention, the 4first step comprises 6 forminga continuous straight tube of any desired length of a cross section,such as shown by Fig. 2. This straight tube has a relatively thickportion which extends longitudinally of the tube, and the thicknessgradually decreases circumferentially l0 to a point' diametricallyopposite said thick portion.

In other words, as shown in Fig. 2, the thick portion of the tube to bebent lies directly opposite the thin portion, and there is a gradual 16be bent is forced to change in thickness between these portions,.the

inner face of the tube being eccentric to the outer face. After the tubehas been forced through the curved passageway I2, it is curved as shownat the left of Fig. 1, and it has a uniform thick- 20 ness, as shown inFig. 3. 'I'his uniformity in thickness of the bent tube is due partly tothe non-uniformity in thickness of the material to bepbent, and partlyto the upsetting operation which occurs when the tube is bent.

Il designates a stationary guide tube (Fig. 1) extending from theentrance of the curved passageway I2 and conforming to the outer face ofthe straight portion of the tube I3. A heating chamber I5 surroundingthe guide tube I4 may be 30 covered with insulation I Ii and providedwith inlet and exhaust pipes I'l and I8 for the admission anddischarge-of the heating medium, which may be a highly heated gas orother suitable heating agent. 'Ihe heat transmitted from this 35 chamberI5 may be great enough to, subject the tube I3 to a substantiallyuniform red heat while it passes through the guide tube I4.

The thickest portion of the tube I3 passes from the guide tube I4 to thecurve of largest radius in 40 the curved passageway I2, as shown in Fig.1, while the thinnest portion in said tube passes through the curve ofshortest radius in said pas- Sageway.

The tube la may be pushed through the giuda, 45 I4 by any suitable powerand is gradually heated to a uniform high temperature by the heattransmitted from the surrounding chamber I5.'

A local cooler I9 is located at the entrance to the` 50 curvedpassageway I2 so that the thickest portion of the tube to be bent issubjected to a Acooling action as it passes to the bending zone in thecurved passageway I2. Y

As shown by Fig. 4, the local cooler Il may be I6 hammer is smaller thanyment from the arms provided with inlet and discharge pipes 28 and 2|through which a cooling fluid is transmitted.

The bending zone in the curved passageway I2 extends approximately fromthe entrance of said passageway to a position near the point designatedby 22. The curved passageway is preferably tapered as suggested bydimensions appearing in Fig. 1. It is larger in diameter at the bendingzone than the diameter of the tube to be bent, and slightly smaller indiameter beyond the bending zone than the diameter of the passageway atthe bending zone.

The decrease in diameter of the passageway I2 beyond the bending zonewill eliminate the slight flattening which occurs at the inner arc ofthe tube where the pressure tends to force the tube away from the faceof the die, and this feature also provides the tube with a smooth anduniform circular outer face.

A hammer 23 having a curved portion 24 is located in the curvedpassageway I2. i The hammer is provided with a straight portion 25extending into the straight passageway I4. The diameter of the straightportion 25 of the hammer is approximately equal to the internal diameterof the tube to be bent, and the curved portion 24 of said the internaldiameter of the tube as it passes the curved portion of the hammer.

In the drawings I have shown a device for reciprocating the hammer inthe passageways I2 and I4. However, it is to be understood that anyother suitable means could be used to operate the hammer. l f e Thedevice as shown comprises a rod 26 having a head 21 which is located ina chamber 28 in the straight portion 25 of the hammer, as shown inFig. 1. The head 21 on the rod 26 is adapted to strike the walls 29. and30 of the chamber 28 to force the hammer backward and forward in thepassageways I2 and I4.

The rearward portion of the rod 26 is adapted to receive arms 3| whichare pivotally secured to a shaft 32 and held in position by the collars33. The lower portions of the arms 3| are in the form of hooks 34and, asshown in Fig. 1, these hooks are detachably secured to the rod 26.Collars 35 are located on the rod 26 at opposite sides of the arms 3l toprovide for the transmission of move- 3| to said rod 26.

The shaft 32 is slidably supported in hangers 36- and 31. A spring 38 islocated on the shaft between the hanger 31 and a spring seat 38. Thisspring will tend to hold the shaft 32 and rod 26 in theirrearwardpositions.

To provide for the reciprocation of the shaft 32 and rod 26, I haveshown bevel gears 48 and 4I through whichpower is transmitted from amotor 42 to a carn.43. A collar 44 which is secured to the shaft 32 by aset screw 45, has a projection 46 which lies in the path of the cam 43.As the cam 43 rotates, the extended portion 41 of the cam will force theprojection 46 on the collar together with the shaft 32 and rod 26forwardly, and after the extended portion o'f the cam passes theprojection 46 on the collar, the spring 38 will force the shaft 32 androd 26 to a rearwardposition. Since the hammer 23 is operatively securedvto the lrod 26, it will likewise be reciprocated by the cam 43 andspring 36.

The curved portion 24 of the hammer (Fig. l) is provided with a curvedface 48 conforming to the curvature of the inner face of the arc ofrelatively large radius of the bent tube.

`way I in the rod The curved portion 24V of the hammer is also providedwith another curved face 49 conforming to the curvature of the innerface of the arc of relatively small radius of the bent tube.

The curved face 48 of the hammer provides a cam which forces the tubeonto the curve of largest radius in the curved passageway at thecompletion of the forward stroke of the hammer, and at the same timeforces a portion of the hammer in the straight passageway onto theportion of the tube approaching the bending zone at the are of smallestradius.

The curved face 49 of the hammer provides a cam which forces the tubeonto the curve'of smallest radius in the curved passageway at thecompletion of the rearward stroke of the hammer, and at the same timeforces a portion of the hammer in the straight passageway onto theportion of the tube approaching the bending zone at the arc of largestradius.

shown a passageway 50 extending from the chamber 28 in the hammer to theforward end of the hammer. The rod 26 has a passageway 5|, and

the head 21 on said rod is provided with passageways 52 whichcommunicate with the passageway 5| and the chamber 28. Air or othercooling medium may, therefore, be forced from any suitable source (notshown) through the passage- 26, and through the passageways 52, chamber28 and passageway 58 to provide the desired cooling of the hammer.

The chamber 28 in the straight portion of the hammer is preferablysurrounded by insulation 53 to retard the transmission of heat from theheating chamber I5 to the chamber 28 where the head 21 on the rod 26strikes the walls 29 and 30.

The operation of the parts so far described will be briefly set forth asfollows:

The arms 3| are detached from the shaft 32 and a tube I3 having anexternal diameter of 3.392 and a cross section, suchas shown in Fig. 2,may be placed onto the rod 26. The arms 3| are then replaced in positionand the tube forced by any suitable means (not shown) through thestraight passageway I4 and the curved passageway I2.

Additional tubes I3 may be delivered to the apparatus, as shown bydotted lines in Fig. 6, and the bending operations may be carried outcontinuously for an' indefinite period. Each tube, excepting the rst,pushes a. preceding tube entirely through the bending die, and the benttubes are discharged from the apparatus in the form of elbows, returnbends, or the like, depending upon the length of the straight tubesections delivered to r.the apparatus.

When the tube passes through the straight passageway I4, it may beheated to a substantially uniform red heat by the heat transmitted fromthe heating chamber I5. As the tube passes to the bending zone, thethickest portion of the tube is subjected to a cooling action at thelocal cooler I9 to prevent substantial upsetting of the relatively thickportion of the tube in the bending zone.

When the tube enters the bending zone it is preferably enlarged so thatit will have an externaldiameter slightly greater than 3.5 inches.

When the tube is forced through the bending zone of the curvedpassageway I2, it has a tendency to' depart -from the arcuate faces ofthe To prevent overheating of the hammer, I have to produce a bridgingaction `and thus separate the tube from the inner arc of the curvedpassageway.`v

The hammer 23 is reciprocated while the tube is passing through thebending zone. When the hammer reaches the end of its forward stroke, itscurved face 48 will strike the tube on its inner face at the arc ofrelatively large radius and force this portion of the tube onto therelatively large arc of the curved passageway.

The curved face 48 of the hammer will also provide a cam action on theface of the tube,

to force the straightportion 25 of the hammer onto the' thin portion ofthe tube to p'revent buckling of the relatively hot thin metalapproaching the bending zone.

After the completion of the forward stroke of the hammer 23, the curvedface 48 of the hammer will remain in contact with the inner face of thetube while the head 21 on the rod 28 travels from the wall 29 of thechamber 28 to the wall 39. This period of time, however, is relativelyshort as the spring 38 immediately withdraws the rod 28 when theextended portionof the cam 4,3 passes the projection 46 on theV collar44.

At the completion of the rearward stroke of the hammer 23, the curvedface 49 of the hammer will force metal of the tube at the curve of smallradius onto the face of the curved passageway having a relatively smallradius, to prevent any bridging action which might separate the tubefrom 'the inner or relatively small arc of the die.

The curved face 49 of the hammer 23 will at this time provide a camaction against the inner face of the tube at the arc of relatively smallradius to force the straight portion 25 of the hammer onto the thickstraight portion of thev tube to prevent irregular 'separation of thisportion of the tube from the wall of the straight passageway.

After the completion ofthe rearward stroke of the hammer there is arelatively long time interval during whichthe curved; face 49 ofthe-hammer remains ln. contact with the tube. This interval is due` .tothe fact that the cam must travel a relatively long distancebefore itagain forces the hammer forward.

" 'I'he curved faces 48 and 49 of the hammer conV- form vto thecurvatures desired y,in the bending v, zone. The inner faces of thetuberat the relativelylarge and small arcs wil1therefore, be given thedesired curvature duringthe 'hammer-v ing actionin the bending zone. fIn theform of the invention; disclosed wherein the/tube is`enlarged:inthe bendingzone,A the curved portion-24 .of thereciprocating. hammerl will. aid in ,enlarging theD tube by,i'orcvirng". Vit V ontathewalls of. the curvedmssewy- After Ythe .tubepasses l.from .the bending... zone it isslightlycontracter,igtoa.diameterfofy approxi-. mately-inchesfinthecurved-passageway i2` to.. insure a smooth and; uniform circularouterl face. lWhen the-tubeias .illwitrated*inlilies-.11.y .and passestromfthef. die. .-the=.-w11s fit-they tube;.w1li here a uniformthicknessofpnrasmately02.16, an external diame r,of3`.f5 yand vaninternaidh,

form ofmy invention, andthey ydoritin 'any lway-.3V

1. The' mattei attaquent aived* tutti" tube while forcing the samethrough a curved passageway, hammering the inner face of the arc ofrelatively large radius of the tube `during said bending operation toforce the tube onto the curved face 'of the largest radius in saidpassageway, and hammering the inner face of the arc of relatively smallradius of the` tube during said bending operation to force the tube ontothe curved face of smaller radius in said passageway. 2. 'Ihe method ofproducing curved tubes which comprises heating a tube, bending said tubeand enlarging the diameter thereof while forcing said tube through acurved passageway, hammering the inner face of the arc of relativelylarge radius of the tube during said bending operation to force the tubeonto the face of largest radius in said passageway, hammering the innerface of the arc of relatively small radius of the tube during saidbending operation to force the tube onto the curved face of smallerradius in said passageway to prevent a bridging action of the materialat the curve of smallest radius, and to aid in enlarging the diameter ofthe tube, cooling the relatively thick portion of the tube to check anupsetting action in said thick portion,` and then slightly contractingsaid tube to provide the tube with va substantially smooth and uniformcircular outer face.

3. 'I'he method of producing curved tubes which comprises forming a tubewith a relatively thick portion longitudinally of thetube, the thicknessdecreasing circumferentially to a. point dia metrically opposite saidthick portion, heating said tube, bending said tube and enlarging thediameter thereof by forcing said tube. through a curved passageway, andhammeringD the arcs of relatively large and small radii of the tubeduring said bending operation. I

4. 'Ihe method of producing curved tubes which comprises forming a tubewith a relatively thick portion longitudinally ofthe tube, the thicknessdecreasing circumferentially to a point diametrically opposite saidthick portion, heating said A said bending operation to force the tubeonto the 4 curve of largest radius in said curvedpassageway, hammeringthe inner face of the arc of relatively small radius of the tube duringsaid bending operation lto-vforce the tube onto the curve of smallerradius in said passageway, to prevent a bridging actionof the tube atthe curve of smallest radius and to aid in enlarging the Idiameter ofthe tube, cooling the relatively thick portion of the tube duringsaidbending operation to check an upfsetting, action in said thick portion,and then slightly contracting the diameter of the bent tube to providethe tube with a substantially smooth and runiform circular outer face.

, 5l `In vartube bending. apparatus, a bending die having acurvedpassageway through which the tube. is forced to form the desired bend,said curved passageway having a larger diameter at thefbending zone thanthe diameter of the tube tafbe,v bent, so as to enlarge the tube duringthe bending operation, and means whereby the tube is j-forced yentirelythroughand discharged from saidcurved passageway.

`6...In. a..tube bending apparatus, a bending die having a curvedpassageway through which the tube is forced to form the desired bend, acurved hammer secured within said passageway so as to remain at thebending zone therein, and means whereby said hammer is forced onto theinner face of the bend of largest radius of the tube to forcethe tubeonto the arc of largest radius of the curved passageway.

7. In a tube bending apparatus, a bending die having a curved passagewaythrough which the tube is forced to form the desired bend, a curvedhammer secured within said passageway so as to remain at,the bendingzone therein, and means whereby said hammer is forced onto the innerface of the bend of relatively small radius in the tube to force thetube onto the corresponding portion of the curved passageway.

8. In a tube bending apparatus, a bending die having a curved passagewaythrough which the tube is forced to form the desired bend, a hammersecured in said passageway so as to remain at the bending zone therein,and means whereby said hammer is reciprocated to alternately "force thetube onto oppositely disposed faces of said curved passageway. Y

9. In a tube bending-apparatus, a bending die having a curved passagewaythrough which the tube is forced to form the desired bend, said curvedpassageway having a larger diameter at the bending zone than thediameter of the tube to be bent, said curved passageway being 'slightlysmaller in diameter beyond the bending zone ythan the diameter. of thepassageway at the bending zone, a curved hammer located in said curvedpassageway, said curved hammer being smaller in diameter than theinternal diameter of the tube passing the curved portion of the hammer,and means whereby said hammerI is reciprocated in said passageway, saidcurved hammer providing a cam face adapted to force the tube onto thecurve of largest radius in the curved passage- .way at the completion ofone stroke of the hammer, said `curved hammer also providing a cam faceadapted to force the tube onto the curve of small radius in the curvedpassageway at the completion of another stroke of the hammer.

10. In a tube bending apparatus, a bending die having a curvedpassageway through which the tube is forced to form the desired bend, acylindrical housing communicating with said curved passageway, saidcylindrical housing having a straight passageway conforming to theexternal diameter of the tube to be bent, a hammer having a curvedportion located in said curved passageway, said hammer being providedwith a straight portion extending into said straight passageway, thediameter of said straight portion of the hammer being approximatelyequal to the internal diameter of the tube to be bent, the curvedportion of said hammer being smaller in diameter than the internaldiameter of the tube passing the curved portion of the hammer, and meanswhereby said hammer is reciprocated in said passageways, said curvedhammer providing a cam face adapted to force the tube onto the curve oflargest radius in the curved passageway at the completion of the forwardstroke of the hammer while forcing a portion of the hammer in thestraight passageway onto the portion of the tube approaching the bendingzone at the arc of smallest radius, said curved hammer also providing acam face adapted to force the tube onto the curve offrelatively smallradius in the curved passageway while forcing a portion of the hammerinthe straight passageway onto the portion of the tube approaching thebending zone at the are of largest radius. I

11. Ina tube bending apparatus, a bending die disposed faces of saidcurved passageway.

vhaving a curved passageway through which the tube is forced to form thedesired bend, a cylindrical housing communicating with said -to be bent,said curved passageway being slightly smaller in diameter beyond thebending zone than the diameter of the passageway-at the bending zone, ahammer having a curved portion located in said curved passageway, saidhammer being provided with a straight portion extending into saidstraight passageway, the diameter of said straight portion of the hammerbeing approximately equal to the internal diameter of the tube to bebent, the curved portion of said hammer being smaller in diameter thanthe internal diameterof the tube passing the curved portion of thehammer, and means -whereby said hammer is reciprocated in saidpassageways, said curved portion of the hammer including a cam faceadapted to force the tube onto the curve of largest radius in the curvedpassageway at the completion of the forward stroke of the hammer whileforcing av portion of the hammer in the straightpassageway at thecompletion of the rearward stroke of the hammer and to force a portionof the hammer in the straight passageway onto the portion of the tubeapproaching the bending zone at the arc of largest radius.

12. The ,method of producing curved tubes which comprises bending atraveling tube while forcing successive portions of said tube entirelythrough a curved bending zone to form a curved bend in the tube, and atthe same time forcibly smoothing successive portions of the curved bendby transmitting them from said curved bending zone, through acorrespondingly curved contracting zone and forcibly reducing thediameter of said curved bend as it travels through said curvedcontracting zone, said curved bend being transmitted entirely throughsaid curved contracting zone to produce ,a curved tube having asubstantially smooth and uniform outer face.

13. 'I'he method of producing curved tubes which comprises bending andincreasing the diameter of a traveling tube while forcing successiveportions of said tube entirely through a curved bending zoneC to. form acurved bend in the tube, and at the same time forcibly smoothingsuccessive portions of the curved bend by transmitting them from saidvcurved* bending zone, through a correspondingly curved contracting zoneand forcibly reducing the diameter of said curved bend as it travelsthrough said curved contracting zone, said curved bend being transmittedentirely through said curved contracting zone to produce a curved tubehaving a substantially smooth and uniform outer face.

14. The method of producing curved tubes which comprises bending a tubeby forcing it through a curvedpassageway, and 'continually hammering theinner face of the tube during the bending operation by striking hammerblows on the curves of relatively large and small radii formed in thebent portions of the tube, so as to hammer said bent portions onto theopposltely l 1,996,838 15. The method of producing curved tubesv whichcomprises bending a tube by forcing it entirely through a curvedpassageway, and continually hammering the inner face of the tube bystriking alternate hammer blows on the curves of relatively large andsmall radii formed in the -oppositely disposed bent portions of thetube, so-

as to alternately hammer said bent portions onto the oppositely disposedfaces of said curved passageway.

16. In a tube-bendingapparatus, a bending die having a curved passagewayincluding an arcuate bending zone into which the tube is forced to forma correspondingly curved bend and an arcuate contracting zone throughwhich the curved bend is discharged, said curved passageway-beingcontracted beyond said bending zone to reduce the diameter of the curvedbend as it passes through said arcuate contracting zone.

17. In a tube-bending apparatus, a bending die having a curvedpassageway including an arcuate bending zone into which the tube isforced to form a correspondingly curved bend and an arcuate contractingzone through. which the curved bend is discharged, the diameter of thebending zone in said curved passagewayV being larger than the diameterof the tube to be bent, and said curved passageway being contractedbeyond said bending zone to reduce the diameter of the curved bend as itpasses through said arcuate contracting zone.

LESTER Wr SNELL.

